Port 8448 (TCP) — Matrix federation: what it is, how to check

Port 8448 Matrix federation · TCP

Matrix server-to-server federation. A homeserver that should talk to other Matrix servers needs this reachable (or a .well-known delegation to 443).

Port	8448
Transport	TCP
Service	Matrix federation
Category	Chat and messaging
Range	registered (1024–49151)
Encrypted	Yes, always (TLS or equivalent)
Exposure	Designed to face the internet

What runs on port 8448

Matrix server-to-server federation. A homeserver that should talk to other Matrix servers needs this reachable (or a .well-known delegation to 443). Client traffic uses 443; 8448 is federation only.

Software that uses it: Synapse · Dendrite · Conduit/Conduwuit

Should port 8448 be open?

Designed to face the internet. This port exists to be reachable from anywhere, so the usual question is not whether to open it but how the service behind it is configured and patched.

federationtester.matrix.org checks the whole chain: DNS, .well-known, TLS and the port.

Check port 8448

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :8448'
sudo lsof -i :8448

# from another machine: is it reachable?
nc -zv host 8448
nmap -p 8448 host
curl -v telnet://host:8448      # raw TCP connect test, Ctrl-C to leave

A port that answers from the internet when it should not is the finding; nmap from a machine outside your network (or a VPS) is the honest test, because scans from inside the LAN pass the firewall you are trying to verify.

Allow or block port 8448

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 8448 proto tcp
sudo ufw deny 8448/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 8448 accept
nft add rule inet filter input tcp dport 8448 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 8448 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8448 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=8448 protocol=tcp accept'

Replace 10.0.0.0/8 with the networks that need access. Allowing by source address is the rule that matters; "allow 8448" with no source is just "open".

Related ports

Part of the port number reference. Ports are 16-bit numbers; see also the subnet calculator and the packet decoder, which shows ports inside TCP and UDP headers.

Questions

Is port 8448 TCP or UDP?

TCP. Matrix federation is a connection-oriented protocol; there is no UDP service on 8448 by default (a scanner reporting UDP 8448 open is usually seeing a filtered port).

Is port 8448 encrypted?

Yes, always (TLS or equivalent). The port number does not make it safe by itself: certificate validation, authentication and patching still decide.

How do I check whether port 8448 is open?

On the server, ss -ltnp (or -lunp for UDP) shows whether something listens on 8448 and which process. From another machine, nc -zv host 8448 or nmap -p 8448 host tests reachability. "Open" in a scan means something answered; a firewall usually makes the port filtered (no answer) rather than closed (RST).

Can Matrix federation run on a different port?

Yes; the number is a convention, not a requirement. Changing it reduces log noise from scanners but does not add security, and every client, firewall rule and monitoring check then needs the new number. Keep the default unless you have a concrete reason.